1. Field of the Invention
The present invention relates to a suction device used for an internal combustion engine for distributing intake air to each cylinder of the internal combustion engine. More particularly, the present invention relates to a suction device used for an internal combustion engine capable of enlarging an amount of compaction for absorbing an impact.
2. Description of the Related Art
Conventionally, the prior art related to a suction device used for an internal combustion engine is disclosed in Japanese Unexamined Patent Publication No. 8-193546 and Japanese Patent No. 2887873. Japanese Unexamined Patent Publication No. 8-193546 discloses a technique by which intake air is evenly distributed to each cylinder of an internal combustion engine and the generation of suction noise, that is, the generation of a rumbling noise, which is an unpleasant noise transmitted into a passenger compartment when an automobile is accelerated, is reduced. Further, Japanese Patent No. 2887873 discloses a technique by which a necessary intake air passage length is ensured when a suction manifold is formed into a U-shape.
In this connection, the technique disclosed in the above Japanese Unexamined Patent Publication 8-193546 has the following disadvantages. Since the profile and state of connection of a throttle passage (first chamber) connected with a throttle body are complicated and also the profile and state of connection of a surge tank (second chamber) are complicated, the number of components is increased in the process of resin molding. Therefore, it is difficult to reduce the manufacturing cost. Further, since an air current is not smooth, the air resistance is so high that a loss of the engine output occurs. Furthermore, as it is necessary to provide a space for arranging a suction device in a cylinder head portion of an internal combustion engine (multiple cylinder engine), it is impossible to decrease the height of an engine compartment. Furthermore, it is difficult to provide a suction manifold passage length variable control system by which the air charging efficiency can be enhanced, in the engine speed range from low to high, when a passage length of a suction manifold is varied according to a running state of the internal combustion engine.
Japanese Patent No. 2887873 has the following disadvantages. Each lower branch tube of the suction manifold is formed into a U-shape, from the surge tank. Therefore, length of the passage of the suction manifold is extended. However, since the space in which components are arranged is limited, it is impossible to gently curve the U-shaped portion. Accordingly, the air resistance becomes high, which causes a loss of the engine output.
The present invention has been accomplished to solve the above problems. It is a task of the present invention to provide a suction device used for an internal combustion engine characterized in that: intake air can be evenly distributed to each cylinder of the internal combustion engine while the resistance of a current of intake air is being reduced, the suction device can be easily mounted on a vehicle; and the air charging efficiency can be enhanced according to a running state of the internal combustion engine.
Also, there is conventionally provided an independent fuel injection system in which an injector (fuel injection valve) and a fuel tube are arranged close to a connecting section of a suction manifold of a suction device with an internal combustion engine and fuel is independently injected from a respective injector (fuel injection valve) into each cylinder of the internal combustion engine, which is called MPI (Multi Point Injection).
In this case, the following situation is envisaged. A suction manifold of a suction device used for an internal combustion engine is arranged laterally with respect to the running direction of a vehicle and connected onto the front side of the internal combustion engine, and an impact force is given to the suction device from the front of the vehicle. In this case, the following problems may be encountered. When the suction manifold is deformed, an excessively large deformation is generated in the connecting section of a fuel tube. Therefore, an engagement section of the injector with the suction manifold is damaged or the leakage of fuel is caused by the buckling of the fuel tube.
In order to solve the above problems, Japanese Patent No. 2699915 discloses the following technique. A suction device (suction manifold block) of an internal combustion engine is connected with an outside of the internal combustion engine which arranged laterally with respect to the running direction of a vehicle. There is provided a fragile section, which extends in the axial direction of the suction manifold, in this suction device. In the case of a car collision, this fragile section of the suction manifold is broken, so that an impact force of the car collision is absorbed, and a horizontal cross section of the suction manifold is crushed, so that an occupied cubic volume is decreased and the amount of compaction of the suction device is increased.
That is, in the case of a car collision, the fragile section of the suction manifold is broken, so that the impact force can be absorbed, and the horizontal cross section is crushed and the occupied cubic volume is decreased. In this way, the amount of compaction can be increased.
In this connection, the above structure has the following disadvantages. Since the fragile section is arranged in a portion of the suction manifold which is easily broken by an impact force caused by a car collision, the mechanical strength of this fragile section of the suction manifold is not sufficiently high against external vibration and internal pressure fluctuation when this suction device is normally used.
The present invention has been accomplished to solve the above problems. It is a task of the present invention to provide a suction device used for an internal combustion engine characterized in that the mechanical strength for external vibration and internal pressure fluctuation, which are caused when the suction device is used in a normal state, is sufficiently high while a partial fragile section is not provided in the suction device; and a predetermined portion of the suction device is broken in the case of a car collision so that an impact force caused by the car collision can be absorbed.
A suction device used for an internal combustion engine of the first embodiment of the present invention is composed as follows. The suction device includes a throttle passage, a surge tank and suction manifolds which are arranged from an upstream side to a downstream side. On the downstream side of the throttle passage, there is provided an air connector which is arranged in the longitudinal direction on a side wall face of the surge tank. This air connector is arranged on a wall face corresponding to a position which is substantially a center of the suction manifold which opens to the surge tank. Due to the above structure, intake air can be evenly distributed from the air connector to each suction manifold via the surge tank. In the suction device of the internal combustion engine, when the position of the opening section of the air connector with respect to the surge tank is determined as described above, the length of the passage of the suction manifold including the surge tank can be made equal. Therefore, a rumbling noise (suction noise) can be suppressed.
In the suction device used for an internal combustion engine of the second embodiment of the present invention, the air connector is embedded on a wall face corresponding to a position which is substantially the center of an opening at which the suction manifold is open to the surge tank. Therefore, a total height of the air connector and the surge tank can be reduced.
In the suction device used for an internal combustion engine of the third embodiment of the present invention, the suction manifold is formed from the surge tank to the suction port in such a manner that the suction manifold substantially encircles the outer circumferential wall faces of the air connector and the surge tank. Therefore, in the suction manifold, it is possible to ensure a passage of an appropriate length for obtaining the air charging efficiency corresponding to a running state of the internal combustion engine. Due to the above structure, it is possible to increase an output of the internal combustion engine.
In the suction manifold of the suction device of the internal combustion engine of the fourth embodiment of the present invention, at least one portion on the wall face of the suction manifold is commonly used in the suction manifold and the surge tank. Therefore, volumes of the surge tank and the suction manifold can be increased. Due to the above structure, air resistance can be reduced without increasing the size of the suction device. Therefore, the air charging efficiency for each cylinder of the internal combustion engine can be enhanced.
In the fifth embodiment of the present invention, the suction manifold is open inward on one of the side walls of the surge tank and extended in such a manner that the suction manifold encircles at least an outer circumferential wall face from the side wall face to the other side wall face on the opposite side. Therefore, the radius of curvature of the suction manifold can be made sufficiently large. Accordingly, air resistance can be reduced to as small as possible. Due to the foregoing, the suction device used for an internal combustion engine can be easily mounted on a vehicle, and an engine output of the internal combustion engine can be increased.
According to the suction device used for an internal combustion engine of the sixth embodiment of the present invention, wall thickness in the circumferential direction of the wall section forming the suction passage is substantially uniform, that is, the suction device does not have a partial fragile portion. Therefore, a sufficiently high mechanical strength can be exhibited with respect to external vibration and fluctuation of internal pressure when the suction device is normally used. Since wall thickness in the circumferential direction of the wall section which is substantially perpendicular to the running direction of the vehicle is smaller than wall thickness in the circumferential direction of the wall section which is substantially horizontal to the running direction of the vehicle, an impact force can be absorbed by a breakdown of the wall section which is substantially perpendicular to the running direction of the vehicle in the case of a car collision. Therefore, deformation of the wall section which is substantially horizontal to the running direction of the vehicle can be reduced to as small as possible. For example, damage given to the injector and the fuel tube, which are attached to the wall section of the connecting section with the internal combustion engine, can be reduced.
In the wall section in the suction device used for an internal combustion engine of the seventh embodiment of the present invention, when the suction device is given an impact force from the front in the case of a car collision, a breakdown is caused in a transition region which is formed from a portion substantially perpendicular to the running direction of the vehicle, the cross section of which is formed into a substantial semicircle, to a portion substantially horizontal to the running direction of the vehicle. Due to the foregoing, deformation of the wall section of the connecting section of the suction device with the internal combustion engine can be reduced to as small as possible.
The present invention will be more fully understood from the description of preferred embodiments of the invention set forth below, together with the accompanying drawings.